Conventionally, digitization of data has enabled easy handling of various information such as music, sounds and images by a personal computer, mobile computer and the like. An audio codec technique and a video codec technique have realized band compression of such information, and an environment for easily and efficiently distributing the information to various communication terminal devices via digital communication or digital broadcasting is almost complete. For example, audio and video data (AV data) can be received outdoors by a portable telephone.
Since networks suitable for home or a small region have been proposed, transmitter-receiver systems for data are used for various purposes. As such network systems, various next-generation wireless systems attract attention such as a narrow-band radio communication system with a 5-GHz band as proposed in IEEE802.11a, a radio LAN system with a 2.45-GHz band as proposed in IEEE802.11b, or a short-distance radio communication system called Bluetooth.
In a transmitter-receiver system for data, using such a wireless network system effectively, it is possible to transmit and receive various data easily at various places such as home or outdoors and without using repeaters, and to access and transmit/receive data to/from the Internet.
Meanwhile, for a transmitter-receiver system for data, it is essential to realize a communication terminal device that is small-sized, light-weight and portable and has the above-described communication function. In the communication terminal device, since modulation/demodulation processing of analog high-frequency signals must be performed in a transmitter-receiver unit, generally, a high-frequency transmitter-receiver circuit 100 of a superheterodyne system for converting a transmitted/received signal to an intermediate frequency is provided, as shown in FIG. 1.
The high-frequency transmitter-receiver circuit 100 shown in FIG. 1 has an antenna unit 101 including an antenna and a changeover switch and adapted for receiving or transmitting information signals, and a transmission/reception switching unit 102 for switching transmission and reception. In the high-frequency transmitter-receiver circuit 100, a receiver circuit unit 105 is provided which includes a frequency converter circuit part 103, a demodulator circuit part 104 and the like. In the high-frequency transmitter-receiver circuit 100, a transmitter circuit unit 109 is provided which includes a power amplifier 106, a drive amplifier 107, a modulator circuit part 108 and the like. In the high-frequency transmitter-receiver circuit 100, a reference frequency generator circuit unit is provided which supplies a reference frequency to the receiver circuit unit 105 and the transmitter circuit unit 109.
Although not described in detail, the high-frequency transmitter-receiver circuit 100 of the above-described structure has a very large number of components including various filters inserted between individual stages, large functional components such as a voltage controller oscillator (VCO) and a surface acoustic wave (SAW) filter, and passive components such as inductors, resistors and capacitors proper to a high-frequency analog circuit like a matching circuit or bias circuit. Therefore, the high-frequency transmitter-receiver circuit 100 has a large size as a whole, which is a big problem in reducing the size and weight of the communication terminal device.
In the communication terminal device, a high-frequency transmitter-receiver circuit 110 of a direct conversion system for transmitting and receiving information signals without converting them to an intermediate frequency, as shown in FIG. 2, may also be used. In the high-frequency transmitter-receiver circuit 110, an information signal received by an antenna unit 111 is supplied to a demodulator circuit unit 113 via a transmission/reception switching unit 112 and baseband processing is directly performed. In the high-frequency transmitter-receiver circuit 110, an information signal generated by a source is directly modulated to a predetermined frequency band by a modulator circuit unit 114 without being convened to an intermediate frequency and is then transmitted from the antenna unit 111 via an amplifier 115 and the transmission/reception switching unit 112.
In the high-frequency transmitter-receiver circuit 110 of the above-described structure, since it is constructed to transmit and receive an information signal by performing direct detection without converting the information signal to an intermediate frequency, the number of components such as filters can be reduced and the overall structure is simplified. Therefore, a structure similar to one chip is expected. However, also in the high-frequency transmitter-receiver circuit 110, it is necessary to consider a filter or matching circuit arranged on a latter stage. In the high-frequency transmitter-receiver circuit 110, since amplification is performed once at a high-frequency stage, it is difficult to acquire sufficient gain and an amplification operation must be performed also in a baseband part. Therefore, the high-frequency transmitter-receiver circuit 110 has a problem that a DC offset cancellation circuit and a low-pass filter are needed, increasing the overall power consumption.
Whether the superheterodyne system or the direct conversion system, the conventional high-frequency transmitter-receiver circuit does not have sufficient properties to meet the requirements such as reduction in size and weight of the communication terminal device. Therefore, for the high-frequency transmitter-receiver circuit, various attempts are made to construct a small-sized module using a simple structure based on, for example, a Si-CMOS circuit or the like. One such attempt is a method for manufacturing a so-called one-chip high-frequency circuit board, for example, by forming a passive element with good properties on a Si substrate, constructing a filter circuit, a resonator and the like on an LSI (large-scale integrated circuit) and also integrating a logic LSI of a baseband part.
In such a one-chip high-frequency circuit board, how to form an inductor 120 having good performance is extremely important, as shown in FIG. 3. In this high-frequency circuit board, a large recess part 124 is formed corresponding to an inductor forming part 123 in a Si substrate 121 and a SiO2 insulating layer 122. In this high-frequency circuit board, a first wiring layer 125 is formed in such a manner that it is exposed to the recess part 124, and a second wiring layer 126 is formed on the SiO2 insulating layer 122, thus forming a coil part 127. Moreover, in the high-frequency circuit board, as another feature, a part of the wiring pattern is lifted up in the air from the surface of the substrate, thus forming the inductor 120.
In this high-frequency circuit board, since the process of forming the inductor includes many steps and is complex, there is a problem of increase in the manufacturing cost. In this high-frequency circuit board, electrical interference of the Si substrate existing between a high-frequency circuit unit of an analog circuit and a baseband circuit unit of a digital circuit may become a large problem.
As high-frequency circuit boards that overcome the above-described problems, a high-frequency module device 130 using a Si substrate, as shown in FIG. 4, and a high-frequency module device 140 using a glass substrate, as shown in FIG. 5, are proposed.
In the high-frequency module device 130 shown in FIG. 4, a Si substrate is used as a base board 131. After a SiO2 layer 132 is formed on the base board 131, a passive element layer 133 is formed by a thin film forming technique such as a lithography technique. In the high-frequency module device 130, though described in detail, a wiring layer 134 and passive element parts 135 such as inductors, resistors and capacitors are formed in a multilayer structure via insulating layers 136 in the passive element layer 133.
In the high-frequency module device 130, terminal parts 137 connected with the wiring layer 134 through via-holes (through-holes) are formed on the passive element layer 133, and functional elements 138 such as high-frequency ICs and LSIs are mounted on these terminal parts 137 by a flip-chip mounting method or the like. In this high-frequency module device 130, for example, as it is mounted on a mother board or the like, the high-frequency circuit unit and the baseband circuit unit are discriminated and electrical interference of these circuit units is restrained.
Meanwhile, in this high-frequency module device 130, since the base board 131 is an electrically conductive Si substrate, when forming the passive element parts 135 in the passive element layer 133, the base board 131 may disturb good high-frequency characteristics of the passive element parts 135.
In the high-frequency module device 140 shown in FIG. 5, a glass substrate is used as a base board 141 in order to solve the problem of the base board 131 in the above-described high-frequency module device 130 shown in FIG. 4. Also in the high-frequency module device 140, a passive element layer 142 is formed on the base board 141, for example, by a thin film forming technique or the like. In the high-frequency module device 140, though not described in detail, a wiring layer 143 and passive element parts 144 such as inductors, resistors and capacitors are formed in a multilayer structure via insulating layers 145 in the passive element layer 142.
In the high-frequency module device 140, terminal parts 146 connected with the wiring layer 143 through via-holes are formed on the passive element layer 142, and functional elements 147 such as high-frequency ICs and LSIs are mounted on these terminal parts 146 by a flip-chip mounting method or the like. In this high-frequency module device 140, since a non-conductive glass board is used as the base board 141, capacitive coupling of the base board 141 and the passive element layer 142 is restrained and a passive element part 144 having good high-frequency characteristics is formed in the passive element layer 142. In this high-frequency module device 140, for example, for mounting on a mother board or the like, terminal patterns are formed on the surface of the passive element layer 142 and connection with the mother board is made by a wiring bonding method or the like.
In these high-frequency module devices 130, 140, the passive element layers 133, 143 of high accuracy are formed on the base boards 131, 141, as described above. When performing thin film formation of the passive element layers on the base boards 131, 141, heat resistance to a rise in the temperature of the surface at the time of sputtering, maintenance of the depth of focus at the time of lithography, and contact alignment property at the time of masking are necessary.
Therefore, the base boards 131, 141 must be flattened highly accurately and need to have insulation property, heat resistance, chemical resistance and the like. Since the above-described base boards 131, 141 are Si and glass boards, they have such properties and therefore enable formation of passive elements with low loss at a low cost in a separate process from LSI formation.
In the above-described high-frequency module devices 130, 140, the base boards 131, 141 enables formation of passive elements of high accuracy, compared with a pattern forming method based on printing, which is used in the conventional ceramic module technique, or a wet etching method for forming a wiring pattern on a printed wiring board. The base boards 131, 141 also enable reduction in the size of elements to approximately 1/100 of the area. In the high-frequency module devices 130, 140, by using Si and glass substrates as the base boards 131, 141, it is possible to increase the threshold frequency of the passive elements to 20 GHz or higher.
In these high-frequency module devices 130, 140, pattern formation for a high-frequency signal system and formation of supply wirings such as power source and ground or signal wirings for a control system are carried out via the wiring layers 134, 143 formed on the base boards 131, 141 as described above. Therefore, in the high-frequency module devices 130, 140, problems arise such as occurrence of electrical interference between the wirings, increase in the cost due to the formation of the wiring layers in the multilayer form, and increase in the size due to the arrangement of the wirings.
In these high-frequency module devices 130, 140, there is also a problem of increase in the cost due to the user of relative expensive Si and glass substrates as the base boards 131, 141.
These high-frequency module devices 130, 140 are mounted as so-called one-chip components on a major surface of a mother board 150, as shown in FIG. 6. Here, the high-frequency module device 130 is used for the description.
On one side of the mother board 150, the high-frequency module device 130 is mounted and also a shield cover 151 made of an insulating resin or the like covering the entire high-frequency module device 130 is mounted. On the front and back sides of the mother board 150, pattern wirings, input/output terminal parts and the like are formed and many land parts 152 are formed around the region where the high-frequency module device 130 is mounted.
In the case of mounting the high-frequency module device 130 on the mother board 150, the wiring layer 134 of the high-frequency module device 130 and the land parts 152 are electrically connected by wires 153, using a wire bonding method, so that power supply to and transmission of signals to/from the high-frequency module device 130 are performed. Also the high-frequency module device 140 is similarly mounted on the mother board 150.
With the high-frequency module device 130 mounted on the mother board 150, as the passive element layer 133 is arranged on the mother board 150 via the base board 131, there is a problem of increased size in the direction of thickness.
Moreover, with the high-frequency module device 130 mounted on the mother board 150, it is difficult to provide a wiring structure within the base board 131 and many land parts 152 for supplying power are arranged around the high-frequency module device 130. Therefore, there is a problem of increased size in the planar direction.
As means for solving such problems, a high-frequency module device 160 as shown in FIG. 7 or the like is proposed (see JP-A-2002-94247).
In this high-frequency module device 160, flattening processing is performed on a major surface of a base board 161 made of an organic wiring board or the like, and a high-frequency element layer part 162 having passive elements is formed on the highly flattened major surface of the base board 161 by a thin film forming technique or the like.
In the high-frequency module device 160 of this structure, since electricity and signals can be supplied to the high-frequency element layer part 162 by the base board 161, which is an organic wiring board, without using the wires 153 in the case of the above-described high-frequency module device 150, highly regulated power supply can be carried out. Moreover, in this high-frequency module device 160, since the base board 161 is an organic wiring board, the cost can be reduced compared with the case of using a Si substrate or glass substrate as the base board.
In the above-described high-frequency module device 160, the high-frequency element layer part 162 is sequentially stacked and formed on one side of the base board 161. Since the high-frequency element layer part 162, which takes a high manufacturing cost, is formed on the entire major surface of the base board 161, it is difficult to realize miniaturization and reduction in cost.